Is a waste heat recovery system right for you?
Industrial processes that require large amounts of heat can recoup some of their energy costs by recovering heat to generate electricity
Inside the glowing orange heart of a giant kiln, limestone is fired at 1800° C to create cement. While the cement leaves to go into buildings and roads, the leftover heat is often vented out a flue as hot as 400° C. Should this heat also be put to use?
The US Department of Energy estimates that 20-50 percent of fuel input is lost as heat. In a recent study, this equals 1.5 quadrillion BTUs of recoverable waste heat across eight key domestic industries, equivalent to the energy supplied by 35 full sized power plants.
Aside from desires to improve environmental performance, some companies are starting to discover the business case for using waste heat to generate power. This can be done by two approaches: mechanical processes, where heat is captured and used to spin a turbine, and direct conversion of heat to electricity.
Industries with heat-intensive processes such as ethylene cracking, iron and steel making, cement kilns and glass making can often save money by using a waste heat recovery system to generate their own power, as opposed to venting the excess heat and purchasing equivalent power from the grid.
The cost of kiln fuel for one large cement plant can be as much as 30 percent of its operating cost, while power to run the process is around 12 percent. Installing a waste heat recovery system could offset as much as a third of operating power costs. Given that the annual energy costs of such a site could be more than $17 million, there is a clear return and simple payback for such investments.
At the same time, process industries can be wary of adopting these technologies. They might feel that operating an in-house power plant is outside their core competence, or that it would require additional staff and maintenance resources.
The reality is that many waste heat recovery systems are fully automated and can be integrated into the existing process control systems without an additional operator. There might also be incentives available, as waste heat is considered a renewable energy source.